What defines a cycle on a jet engine?

Lnafziger
  • What defines a cycle on a jet engine? Lnafziger

    Is there a legal definition of a "cycle" on a jet engine?

    We must log the cycles, and some maintenance is determined by cycles. From my understanding, this is partially because of the thermal dynamics of an engine cooling and then reheating, and partially because full takeoff power is used.

    The "usual" time that you log a cycle is when an engine is started and the aircraft then takes off (using full rated takeoff power), but what about unusual situations like:

    • Engine shutdown and restarted in flight
    • Engine started, aircraft takes off, and then returns for a low pass or a touch and go: Would this be two cycles (does it depend on the amount of power used during the touch and go?)?
    • Engine started and then shut down without a flight

  • A cycle is a start to a shutdown. Lets say there is a flight that is loaded with pax, bags, and fuel. They push back and start both engines since the weather is good and their at an outstation. As they taxi to the departure runway, BAM, ground calls up saying there is a groundstop for the hub and its going to be about 30 minutes. The flight pulls into some empty ramps space, and shuts down both engines. Groundstop lifts, both engines started again, and the flight departs. After landing, pulling into the gate, and shutting down the engines, we can say that for this flight, each engine went through two cycles. ALL of this info is logged and maintenance can access it. With some of the newer engines and higher service packages, OEM

  • According to the FAA in AC33.70-1:

    (b) The applicant should validate and maintain the accuracy of the engine flight cycle over the life of the design. The extent of the validation depends on the approach taken in the development of the engine flight cycle. For example, a conservative flight cycle where all the variables are placed at the most life damaging value would require minimum validation. A flight cycle that attempts to accurately represent the actual flight profile, but is inherently less conservative, would require more extensive validation. Applicants may apply further refinements to the engine flight cycle when significant field operational data is obtained.

Related questions and answers
  • dynamics of an engine cooling and then reheating, and partially because full takeoff power is used. The "usual" time that you log a cycle is when an engine is started and the aircraft then takes off (using full rated takeoff power), but what about unusual situations like: Engine shutdown and restarted in flight Engine started, aircraft takes off, and then returns for a low pass or a touch and go: Would this be two cycles (does it depend on the amount of power used during the touch and go?)? Engine started and then shut down without a flight

  • When I took delivery of a new Cessna 182T last year, I did a test flight for certification purposes. During the test flight we had to perform a power off stall but that didn't go as planned as it was simply impossible to stall. What happened is this: when the airspeed dropped well below the power off stall speed we simply started to sink slowly with a nose-high attitude at about 35 KIAS. This "mushing" went on for what seemed ages before I eventually applied power and pushed the nose down to gain airspeed again. We tried it again after that and the same thing happened. I had an instructor

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  • How does autobrake work? Gabriel Brito

    An autobrake is a type of automatic wheel-based hydraulic brake system for advanced airplanes. The autobrake is normally enabled during takeoff and landing procedures, when the aircraft's longitudinal deceleration system can be handled by the automated systems of the aircraft itself in order to keep the pilot free to perform other tasks - Wikipedia How does the aircraft "know" when is time to activate the autobrake systems on a rejected takeoff and landing? Does it apply full brake to all the aircraft's wheels? Is it really used by commercial jets?

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